In contrast to alternating-current networks, natural current zero passage does not take place with direct current. Arcing chambers in direct-current switching devices produce an arcing voltage which is greater than the working voltage, thus forcing the current to zero and dissipating the energy stored in the network. The arcing voltage lies significantly above the working voltage. For example, at a working voltage of 500 V, the appearance of an arcing voltage of 800 V can be expected. However, due to the existing insulation ability of the network, arcing voltage must be limited to a maximum value. Thus, different working voltages require different arcing chambers.
Arcing chambers differ greatly in structure have hitherto been used in direct-current rapid-action switching devices for different working voltages and different switching properties. This entails great structural complexity as well as correspondingly high manufacturing costs.